if you are alone and or vulnerable you would probably qualify for an alert system, a button that you wear around you neck or on your wrist, maybe even voice activated, if you need something you just press a button, this will alert a support line which will open a 2 way communication via your telephone (no you dont need to pick up the telephone, if you are unable to respond then an immediate neighbour may call in or failing that an emergency ambulance will attend.
Its a bit different if you fall and seriously injured and unable to press the button, there are ways around this as well for epileptics etc with motion sensitive equipment.